1. Field
The present application relates to a positioning system, on-board device, and positioning method that perform positioning using positioning satellites.
2. Description of the Related Art
Since it is difficult to accurately measure position by only measuring position based on positioning signals from positioning satellites, such as GPS satellites, a high precision positioning approach is known that employs an augmentation signal from a quasi-zenith satellite. However, the measurement precision falls in cases where it is difficult to receive an augmentation signal from a quasi-zenith satellite, such as due to obstacles. Japanese Unexamined Patent Application Publication No. 2014-173891 accordingly describes an approach to such a problem, in which an augmentation signal from the quasi-zenith satellite is stored in a distribution server, and the augmentation signal stored in the distribution server is distributed over a mobile communication network (internet network) to an on-board unit that performs positioning.
Considering that a vehicle moves at a relatively fast speed, an on-board unit needs to acquire the augmentation signal (hereinafter referred to as a correction signal) with a short cycle. However, when, as described in Japanese Unexamined Patent Application Publication No. 2014-173891, a mobile communication network is utilized, there is a concern about being affected by communication bottlenecks (in communication speed and number of simultaneous communications possible), with a concern that there may be a delay in communication, or an increase in the communication volume. Moreover, an even longer delay occurs in cases where the required correction signal is distributed only after a request has been received. Moreover, for example, for such a correction signal for use in a mobile communication network within Japan, due to the communication system and standards of mobile communication networks differing in other countries to those in Japan, such mobile communication networks cannot be utilized when transmitting such a correction signal, resulting in a need to build new infrastructure.